In factories or the like, a controller for industrial machinery 201 provided with an industrial machinery, such as a robot, has an arrangement, as shown in FIG. 17, wherein a dangerous zone around the industrial machinery (the industrial robot) 203 is enclosed by a safety fence (partitioning means) 207 having a doorway 205 freely opened or closed whereby an operator is prevented from being involved in trouble that the operator is caught in the operating industrial machinery 203. In the case of normal operation of the industrial machinery 203, the operator standing outside the safety fence 207 controls the machinery 203 via a control panel 209 attached to an outside surface of the safety fence 207.
From the standpoint of safety, emergency stop switches 211 are provided at the control panel 209 and at plural places inside and outside of the safety fence 207. In the event of a dangerous state of the industrial machinery 203, any one of the emergency stop switches 211 inside and outside of the safety fence 207 may properly be manipulated to cut off power to a main circuit of the controller 201, thereby driving the whole controller 201 into emergency stop.
From the standpoint of safety, as well, a safety switch 215 is also provided at the doorway 205 of the safety fence 207 so as to deactivate the industrial machinery 203 when a door 213 in the doorway 205 is not fully closed.
The safety switch 215 is electrically connected with the industrial machinery 203 installed at place inside of the safety fence 207 and comprises, as shown in FIG. 18, a switch body 217 containing contacts, and an actuator 219 adapted to close or open the contacts in the switch body 217 when inserted into or extracted from the switch body 217. The switch body 217 is secured to the safety fence 207 at place around the doorway 205, whereas the actuator 219 is secured to the door 213. The actuator 219 is positioned at place corresponding to an insertion hole 221 of the switch body 217 so that the actuator may enter an operation section 223 of the switch body 217 when the door 213 is closed.
The inserted actuator 219 closes the contacts contained in a switch section 225 of the switch body 217, so that the industrial machinery 203 inside of the safety fence 207 is supplied with power and ready to operate. When, on the other hand, the actuator 219 is extracted from the operation section 223 by opening the door 213, the contacts in the switch section 225 are opened to cut off the power to the industrial machinery 203, so that the industrial machinery 203 does operate unless it is manually operated. Thus, the industrial machinery 203 does not operate when the door 213 is open. This leads to the prevention of the occurrence of trouble that the operator working inside of the safety fence 207 is caught in the operating industrial machinery 203.
In cases where the operator enters the zone inside of the safety fence 207 to manually operate the industrial machinery 203 or to carry out maintenance service for the industrial machinery 203, the operator uses a teaching pendant 227 equipped with a push-button switch, a so-called enable switch (deadman switch) in order to obviate an accident associated with contact with the operating industrial machinery 203 during the work.
As shown in FIG. 19, the teaching pendant 227 is a portable unit which is connected with the control panel 209 via a cable 229, thereby enabled to teach a program to the industrial machinery 203 or to operate the industrial machinery 203. The teaching pendant 227 includes an input keyboard 231 disposed on a main surface thereof, and a push-button switch (enable switch) 233 disposed on one side surface thereof. The push-button switch 233 is adapted to be switched from a first OFF state to an ON state, and then to a second OFF state according to the amounts of push-button depression. In some cases, the push-button switch 233 may be disposed on a back side of the teaching pendant 227.
When the teaching pendant 227 is in the first OFF state where a push button 235 of the push-button switch 233 is undepressed, key entry is not effected even though the keyboard 231 is manipulated. When the operator of the teaching pendant 227 teaches a program to the industrial machinery 203, the operator performs the key entry through the keyboard 231 while holding the push-button switch 233 in the ON state by depressing the push button 235. If, at this time, the operator releases the push button 235 recognizing potential danger of contact with any moving part of the manually operated industrial machinery 203, the push-button switch 233 is returned to the initial or first OFF state so that the industrial machinery 203 is deactivated.
In the event of an imminent danger panicking the operator into pressing further down on the push button 235, the push-button switch 233 in the ON state is shifted to the second OFF state, thereby deactivating the industrial machinery 203.
Thus, the teaching pendant 227 permits the key entry via the keyboard 231 thereof only when the push-button switch 233 thereof is in the ON state. Furthermore, the push-button switch 233 can be set to any of the three positions (the first OFF state, the ON state and the second OFF state) according to the amounts of push-button depression 235. Accordingly, the teaching pendant provides for a tangible indication of intent of the operator manually operating the machinery so that the safety of the operator is ensured.
In the manual operation of the industrial machinery 203 as described above, there may be a case where, in addition to the above operator, a plural number of assistant operators enter the zone inside of the safety fence 207 for assisting this main operator manipulating the teaching pendant 227. In this case, these assistant operators individually carry with them a grip type switch device for safety purpose when entering the zone inside of the safety fence 207, the grip type switch device equipped with a three-position type push-button switch of a similar configuration to that of the above push-button switch 233. That is, the industrial machinery 203 can also be deactivated by any of the assistant operators that shifts the grip type switch device to the second OFF state.
A specific example of the grip type switch device is shown in FIG. 20. As seen in the figure, the grip type switch device 239 includes a switch case 241 designed to be held by one hand, and a push-button switch 243 operable as depressed by the hand gripping the switch case 241. The switch device 239 is electrically connected with the aforesaid control panel 209 via a cable 245 connected with contacts in the switch case 241 by soldering and unified with the switch case 241.
The operators inside of the safety fence 207 perform their jobs with one hand thereof while gripping their grip type switch devices 239 in the other hand thereof, respectively. In a case where a program is taught to the industrial machinery 203, the program teaching to the industrial machinery 203 is not effected unless not only the push-button switch 233 of the teaching pendant 227 but also the push-button switches 243 of all the grip type switch devices 239 are shifted to the ON state. This ensures an even more enhanced safety during the work.
Another specific example of the grip type switch device is arranged such that an essential configuration and function of the switch device are substantially the same as those of the above grip type switch device and that a watertight connector is used for removably connecting the contacts in the switch case and the cable.
Since such grip type switch devices 239 are connected with the control panel 209 via the respective cables 245, the operators inside of the safety fence 207 usually carry out their jobs while trailing the cables 245 behind them. Therefore, the cable 245 may be damaged due to sliding contact with the floor or otherwise, a connection portion between the cable 245 and the switch case 241 may be so frequently twisted as to be broken.
Unfortunately, the specific example of the switch device shown in FIG. 20 has the configuration wherein the switch case 241 is unified with the cable 245. Therefore, even though only the cable 245 is damaged, it is impossible to replace the damaged cable alone. Hence, the whole grip type switch device 239 must be changed for the sake of cable replacement. This results in an extremely high maintenance cost.
In the other specific example of the switch device, the cable is connected with the contacts in the switch case via the watertight connector so that the cable alone can be replaced if it is damaged. However, the cable replacement also requires the watertight connector to be replaced. Since the watertight connector itself is quite expensive, a high maintenance cost results, as well.
When the operator performs his job inside the safety fence 207, the door 213 in the doorway 205 is held open whereby the contacts of the safety switch 215 are opened to cut off the power to the industrial machinery 203. However, there may be contemplated a case where the door 213 is inadvertently closed while the operator is working inside the safety fence 207. In such a case, a fear exists that the actuator 219 of the safety switch 215 enters the switch body 217 thereby inadvertently resuming the power supply to the industrial machinery 203.
In view of the foregoing, it is an object of the present invention to provide a grip type switch device wherein, in the case of damage to the cable, the damaged cable alone can be readily replaced at low cost.
It is another object of the present invention to ensure that the industrial machinery is positively maintained in cutoff even if the doorway of partitioning means, such as the safety fence, is inadvertently closed.